(1) Field of the Invention
The present invention relates to a novel polymetalosilazane and a process for the preparation thereof. Silicon-metal-nitrogen-oxygen or silicon-metal-nitrogen-oxygen-carbon ceramics formed by using this polymetalosilazane as the precursor are valuable as heat-resistant high-hardness materials and reinforcing materials for composite materials, and it is considered that these ceramics will be widely utilized in the fields of chemical, metal, aerial, space, precision machinery and automobile industries.
(2) Description of the Related Art
A polymetalosilazane having a silicon-oxygen-metal linkage and/or the structure in which a nitrogen atom and a metal alkoxide are condensed together has not been known.
As the analogous compound, there are known a polytitanocarbosilane prepared by reacting polycarbosilane with a titanium alkoxide and a polyzirconocarbosilane prepared by reacting polycarbosilane with an organozirconium compound (Japanese Unexamined Patent Publication No. 56-74126 and Japanese Unexamined Patent Publication No. 56-92923).
Furthermore, various perhydropolysilazanes and polyorgano(hydro)silazanes prepared by reacting halosilanes with ammonia (Japanese Unexamined Patent Publication No. 60-145903, D. Seyferth et al., "A Liquid Silazane Precursor To Silicon Nitride", Communications of Am. Ceram. Soc., January 1983, Japanese Unexamined Patent Publication No. 60-226890 and Japanese Unexamined Patent Publication No. 61-89230) have been reported.
Ceramics of the Si-M-C-O system (in which M stands for Ti or Zr) obtained by using the polytitano-carbosilane or polyzirconosilane as the precursor contain a free carbon atom. Since this free carbon has a high reactivity with a molten metal such as aluminum and causes degradation of the strength, satisfactory characteristics cannot always be obtained when composite materials are prepared from these ceramics and metals.
Furthermore, when silicon nitride ceramics derived from the polysilazanes are utilized in the form of composite materials with metals, there is a problem of an unsatisfactory affinity with metals.
If these defects are overcome, the utility thereof as a heat-resistant high-hardness material or composite material will be highly improved.